Thunderbolt Performance

The Eagle Ridge Thunderbolt controller is home to two Thunderbolt channels, each one is good for up to 10Gbps in either direction (up or downstream). That works out to be 20Gbps of bandwidth per channel or 40Gbps aggregate between the two. You can only send two channels worth of data down a single Thunderbolt cable, so there's no point to having more than two from a performance standpoint unless you have more than one port on your system.

If DisplayPort and PCIe traffic are indeed carried on separate channels, then the Thunderbolt Display by itself is eating up around 70% of the bandwidth of a single channel on its own (2560 x 1440 x 32bpp x 60Hz with 8b/10b encoding > 6.75Gbps). That leaves 10Gbps in each direction for PCIe traffic. If we look at our benchmarks from the previous section we see that we can hit just under 2Gbps with all of the auxiliary interfaces (GigE, FW800, USB2) running. Given our previous investigation with the Promise Pegasus we know that 8Gbps is feasible there as well. It's possible, that with everything running at once, we could actually run into bottlenecks with Thunderbolt.

To find out I ran a few tests. First I needed a baseline so I threw four SF-2281 SSDs into the Pegasus R6 chassis and configured them in a RAID-0 array. I ran a 2MB sequential read test (QD=16) and measured 909MB/s from the array. This value was obtained without the Thunderbolt Display connected, only the Pegasus R6.

Next I connected the Thunderbolt Display directly to my test MacBook Pro, and then connected the Pegasus to it. I repeated the test, this time getting 900MB/s. Thankfully the presence of the Thunderbolt Display doesn't seem to impact the max data rate I can get from the Pegasus.

For my third test I added a Gigabit Ethernet transfer from a file server to a local SSD using the GigE port on the display. During this test I was also playing back music using the Thunderbolt Display's internal audio codec and speakers. I re-ran the Pegasus test and got 855MB/s.

For my final test I re-ran the third test but added a FireWire 800 to USB 2.0 SSD transfer, both connected to the Thunderbolt Display. I also fired up the FaceTime HD camera on the display using Photo Booth and left it on during the test. The final performance score from the Pegasus was 817MB/s.

Apple Thunderbolt Display Performance

With everything running Thunderbolt performance took a 10% hit. Note that the standard Pegasus configuration isn't able to hit these data rates to begin with, so unless you've pulled out the 12TB of storage and stuck in your own SSDs you won't see any performance drop.

What this does tell me however is the ultra high end users that are looking to daisy chain multiple Thunderbolt storage boxes together may not want to do so. I only have a single Pegasus R6 on hand, but I'm guessing there will be significant performance drop off after the first box. Not that I'm complaining about being able to push nearly 1GB/s over a $49 cable from a notebook, I'm just trying to give a heads up to those who may have aspirations of even higher performance.

Testing the Pieces Display Testing - Color Quality & Uniformity
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  • V4lkyri3 - Friday, September 23, 2011 - link

    Maybe I'm slow to the party, but I'm loving this video review Anand.

    Valkyrie.
    Reply
  • mfenn - Friday, September 23, 2011 - link

    Agreed! Reply
  • GeorgeH - Friday, September 23, 2011 - link

    It was a very well-done video, everything from lighting and sound to the presentation was very well done.

    Hopefully you use video reviews as more of a supplement where it's appropriate though (case reviews with videos would be great.) I can read much faster and than I can listen, and it's much easier to search and reference text.
    Reply
  • dragonsqrrl - Friday, September 23, 2011 - link

    +1! Love the way Anand and reviewers have been using these video's to supplement the written content, it's a great added bonus.

    And I agree, it would be great for things like case, monitor, and smart phone reviews, things of that nature, but not so much for a hard drive or SSD reviews, for instance. And it seems like that's precisely the way the video reviews have been used thus far.

    Great stuff...
    Reply
  • Operandi - Monday, September 26, 2011 - link

    For one it is a very concise version of the full review, and it complements it very well. Just the quick and dirty info on what Apple has been up to, and as this will do nothing for me as a PC user I now know I can stop there; if I want more detailed info I have the full review at my disposal, pretty cool. The other obvious benefit is the video format itself has advantages over still images for products such as this.

    Also great work on the video and audio production, it looked and sounded great. The set is almost too minimalistic though, might want to experiment there.
    Reply
  • tech6 - Friday, September 23, 2011 - link

    +1 - Nice work - looks and sounds professional. More please. Reply
  • leodc - Friday, September 23, 2011 - link

    You are are quite a fluent speaker, Anand! You spoke continuously for more than 5 minutes without meandering, drifting.... Impressive. Reply
  • ImSpartacus - Friday, September 23, 2011 - link

    I agree. I love how he leaped into the anecdote without throwing an annoying intro on the screen. Anand's performance was engaging; I love listening to where he thinks the industry is going. Reply
  • B3an - Friday, September 23, 2011 - link

    It's well made but it annoys me how he puts this much effort in to Apple products and only makes a video of this quality for something by Apple. Also in Anandtech articles theres very often better quality photos for Apple stuff, in comparison to other articles for anything else. More effort is put in to lighting, location, and camera shots. On a whole Apple articles just seem better presented and it just makes the site seem bias and like some fanboyism exists. Reply
  • Stas - Friday, September 23, 2011 - link

    Or they just get paid to do it right. Other articles they do on their own initiative. I'm sure, if a company stepped in and paid for a review, they would do it just as well, as Apple's. Reply

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